SOLUTION: Aki's bicycle designs has determined that when x hundred bicycles are built, the average cost per bicycle is given by c(x)=0.2x²-1.3x+8.181, where c(x) is in hundreds of dollars.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Aki's bicycle designs has determined that when x hundred bicycles are built, the average cost per bicycle is given by c(x)=0.2x²-1.3x+8.181, where c(x) is in hundreds of dollars.       Log On


   



Question 633223: Aki's bicycle designs has determined that when x hundred bicycles are built, the average cost per bicycle is given by c(x)=0.2x²-1.3x+8.181, where c(x) is in hundreds of dollars.
The shop should build_____bicycles.

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
c%28x%29=0.2x%5E2-1.3x%2B8.181 is a quadratic function.
As a quadratic function with a positive coefficient for the term in x%5E2,
it goes through a minimum.
Quadratic functions have the general form
f%28x%29=ax%5E2%2Bbx%2Bc
They graph as parabolas,
and have a minimum or maximum at x=-b%2F2a.
In the case of c%28x%29=0.2x%5E2-1.3x%2B8.181 , there is a
minimum at x=1.3%2F%282%2A0.2%29 --> x=1.3%2F0.4 --> highlight%28x=3.25%29
So the cost per bicycle is minimum when 3.25 hundred bicycles are built.
That is highlight%28325%29bicycles

ABOUT QUADRATIC FUNCTIONS:
For a quadratic function, f%28x%29=ax%5E2%2Bbx%2Bc ,
when the leading coefficient, a, is positive,
the function grows without bounds as x%5E2 increases on both ends (positive and negative),
as the ax%5E2 term overwhelms whatever value the rest of the polynomial could take.
As a consequence the function looks like a smile, with a minimum in the middle:
graph%28200%2C100%2C3%2C9%2C1%2C11%2C%28x-6%29%5E2%2B2%29
If a%3C0 the shape of the graph is flipped and the function has a maximum:
graph%28200%2C100%2C3%2C9%2C-12%2C-2%2C-%28x-6%29%5E2-3%29
The maximum or minimum is the vertex of the parabola.
The function can be transformed algebraically from f%28x%29=ax%5E2%2Bbx%2Bc to
f%28x%29=a%28%28x%2Bb%2F2a%29%5E2-%28b%5E2-4ac%29%2F4a%5E2%29
which shows that the extreme value (maximum or minimum) occurs when
x%2Bb%2F2a=0, when x=-b%2F2a
and the line represented by x=-b%2F2a is the axis of symmetry of the parabola that is the graph of the function.
If the expression reminds you of the quadratic formula, it is no coincidence.
The quadratic formula comes from the same
f%28x%29=a%28%28x%2Bb%2F2a%29%5E2-%28b%5E2-4ac%29%2F4a%5E2%29 making f%28x%29=0 .